In case it is necessary to braze on the inside of a tube or any deep
recess, the spelter may be placed on a flat rod long enough to reach to
the farthest point. By distributing the spelter at the proper points along
the rod it may be placed at the right points by turning the rod over after
inserting into the recess.
_Flux._--In order to remove the oxides produced under brazing heat and
to allow the brazing metal to flow freely into place, a flux of some kind
must be used. The commonest flux is simply a pure calcined borax powder,
that is, a borax powder that has been heated until practically all the
water has been driven off.
Calcined borax may also be mixed with about 15 per cent of sal ammoniac to
make a satisfactory fluxing powder. It is absolutely necessary to use flux
of some kind and a part of whatever is used should be made into a paste
with water so that it can be applied to the joint to be brazed before
heating. The remainder of the powder should be kept dry for use during the
operation and after the heat has been applied.
_Preparing the Work._--The surfaces to be brazed are first thoroughly
cleaned with files, emery cloth or sand paper. If the work is greasy, it
should be dipped into a bath of lye or hot soda water so that all trace of
oil is removed. The parts are then placed in the relation to each other
that they are to occupy when the work has been completed. The edges to be
joined should make a secure and tight fit, and should match each other at
all points so that the smallest possible space is left between them.
Pages:
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194